Help with this geometry question?

I actually got tested on this today! And I got it wrong because I have no idea how to do it. I know that you have to use pythagorean theorem to figure out that the height of the triangle is the square root of 95. You can then find the area of the triangle using the formula A=1/2BH. But I cannot figure out how you find out the radius or diameter of the circle in order to find the area of the circle.But once you figure out how to find the radius, you find the area of the circle using the formula pi times r squared. After, you'd subtract the area of the triangle from the area of the circle and TADA! The answer. I hope this helps a little bit!